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05 500
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Discussion Starter #1
My 2005 500 now has almost 94K on the ODO and she still kicks ass - really, no major issues. The other day I couldn't find my key so I pulled out the spare from it's dungeon. To my surprise, it would not synch with the truck. I used the manual key to open the truck, the alarm came off as expected. However, I was able to start the truck - that was a second surprise to me because I thought these trucks would shut off the motor on any security breach until the alarm was properly turned off. First thought was that the keyfob battery was dead. I replaced it but the fob still would not activate any vehicle function. Obviously there's something wrong with the fob. What can be done? The darn thing has been sitting in my desk drawer for years, undisturbed. So how can it get bad? And, do I don't quite understand the motor shut off thingy when the alarm is on?
 

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2003 ML55 AMG - 2005 E55 AMG
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316 Posts
my 2 cents:

Yes, the alarm is supposed to go away when you turn the key in the ignition. This is the same for all ML vehicles I think. It was even spelled out in my owners manual.

Now, your key fob: could be a couple of things.

1) Sync (sync your key according to your owners manual). if you have done this correctly, and it still will not sync, try this:

2) Open the battery compartment. Check the prongs in the fob, and make sure they make solid contact with the batteries. Perhaps even bend them slightly back.

If none of those things work, there is the possibility, although very small since your other key worked, that your module communicating with your key is bad.

Personally I think step 1 or 2 should do the trick.
 

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Premium Member
05 500
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Discussion Starter #3
my 2 cents:

Yes, the alarm is supposed to go away when you turn the key in the ignition. This is the same for all ML vehicles I think. It was even spelled out in my owners manual.
Thanks for that confirmation - your 2 cents may worth much more my friend, you never know. I certainly missed that educational piece about the security system while I was pretending to read the entire manual.

Now, your key fob: could be a couple of things.

1) Sync (sync your key according to your owners manual). if you have done this correctly, and it still will not sync, try this:

2) Open the battery compartment. Check the prongs in the fob, and make sure they make solid contact with the batteries. Perhaps even bend them slightly back.

If none of those things work, there is the possibility, although very small since your other key worked, that your module communicating with your key is bad.

Personally I think step 1 or 2 should do the trick.
No I haven't tried to synch key per manual and I will do that. The reason I didn't try it is because the spare fob worked just fine the last time I used it. Also, I have since found my regular fob and it works just fine. But this is the ML and it doesn't hurt synching. Again, thanks plenty.
 

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Outstanding Contributor
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
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4,405 Posts
While sitting in your desk drawer, the batteries went flat and your remote unlock circuit-board forgot the code. No worries, just power it back up and your ML can re-learn the new code and position in the sequence. It just needs 5 consecutive codes to work out where it's up to. (or something like that)

The immobilizer chip doesn't need power to remember its stored code, so it will still work after years gathering dust.
 

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05 500
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Discussion Starter #5
...just power it back up and your ML can re-learn the new code and position in the sequence. It just needs 5 consecutive codes to work out where it's up to. (or something like that)...
Can you go into more details? What do I have to do for the ML to relearn the new code? Have the key in the truck or just continue to click on the "door open" button several times? What about the 5 consecutive codes? What's that all about? Thanks.
 

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Outstanding Contributor
2002 ML320, 2003 A160, 2002 ML500, 2018 GLS350d
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4,405 Posts
The detail is in your owner's manual, the part about synching your remote control. Key to position 2, remove it, and within 10 sec hold down lock & press unlock 5 times, then press any button (except 'panic').
 

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05 500
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Discussion Starter #9
The detail is in your owner's manual, the part about synching your remote control. Key to position 2, remove it, and within 10 sec hold down lock & press unlock 5 times, then press any button (except 'panic').
Thanks.
 
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